/*
 * Copyright 2012-2018 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package cn.springcloud.gray.bean.properties;

import java.lang.annotation.Annotation;
import java.lang.reflect.Method;

import org.springframework.beans.BeansException;
import org.springframework.beans.factory.InitializingBean;
import org.springframework.beans.factory.config.BeanPostProcessor;
import cn.springcloud.gray.bean.properties.bind.Bindable;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;
import org.springframework.core.Ordered;
import org.springframework.core.PriorityOrdered;
import org.springframework.core.ResolvableType;
import org.springframework.core.annotation.AnnotationUtils;
import org.springframework.core.env.PropertySources;
import org.springframework.validation.annotation.Validated;

/**
 * {@link BeanPostProcessor} to bind {@link PropertySources} to beans annotated with
 * {@link ConfigurationProperties}.
 *
 * @author Dave Syer
 * @author Phillip Webb
 * @author Christian Dupuis
 * @author Stephane Nicoll
 * @author Madhura Bhave
 */
public class ConfigurationPropertiesBindingPostProcessor implements BeanPostProcessor,
        PriorityOrdered, ApplicationContextAware, InitializingBean {

    /**
     * The bean name that this post-processor is registered with.
     */
    public static final String BEAN_NAME = ConfigurationPropertiesBindingPostProcessor.class
            .getName();

    /**
     * The bean name of the configuration properties validator.
     */
    public static final String VALIDATOR_BEAN_NAME = "configurationPropertiesValidator";

    private ConfigurationBeanFactoryMetadata beanFactoryMetadata;

    private ApplicationContext applicationContext;

    private ConfigurationPropertiesBinder configurationPropertiesBinder;

    @Override
    public void setApplicationContext(ApplicationContext applicationContext)
            throws BeansException {
        this.applicationContext = applicationContext;
    }

    @Override
    public void afterPropertiesSet() throws Exception {
        // We can't use constructor injection of the application context because
        // it causes eager factory bean initialization
        this.beanFactoryMetadata = this.applicationContext.getBean(
                ConfigurationBeanFactoryMetadata.BEAN_NAME,
                ConfigurationBeanFactoryMetadata.class);
        this.configurationPropertiesBinder = new ConfigurationPropertiesBinder(
                this.applicationContext, VALIDATOR_BEAN_NAME);
    }

    @Override
    public int getOrder() {
        return Ordered.HIGHEST_PRECEDENCE + 1;
    }

    @Override
    public Object postProcessBeforeInitialization(Object bean, String beanName)
            throws BeansException {
        ConfigurationProperties annotation = getAnnotation(bean, beanName,
                ConfigurationProperties.class);
        if (annotation != null) {
            bind(bean, beanName, annotation);
        }
        return bean;
    }

    @Override
    public Object postProcessAfterInitialization(Object bean, String beanName) throws BeansException {
        return bean;
    }

    private void bind(Object bean, String beanName, ConfigurationProperties annotation) {
        ResolvableType type = getBeanType(bean, beanName);
        Validated validated = getAnnotation(bean, beanName, Validated.class);
        Annotation[] annotations = (validated != null)
                ? new Annotation[]{annotation, validated}
                : new Annotation[]{annotation};
        Bindable<?> target = Bindable.of(type).withExistingValue(bean)
                .withAnnotations(annotations);
        try {
            this.configurationPropertiesBinder.bind(target);
        } catch (Exception ex) {
            throw new ConfigurationPropertiesBindException(beanName, bean, annotation,
                    ex);
        }
    }

    private ResolvableType getBeanType(Object bean, String beanName) {
        Method factoryMethod = this.beanFactoryMetadata.findFactoryMethod(beanName);
        if (factoryMethod != null) {
            return ResolvableType.forMethodReturnType(factoryMethod);
        }
        return ResolvableType.forClass(bean.getClass());
    }

    private <A extends Annotation> A getAnnotation(Object bean, String beanName,
                                                   Class<A> type) {
        A annotation = this.beanFactoryMetadata.findFactoryAnnotation(beanName, type);
        if (annotation == null) {
            annotation = AnnotationUtils.findAnnotation(bean.getClass(), type);
        }
        return annotation;
    }

}
